The present application claims priority to Japanese Patent Application No. 2001-129252 filed Apr. 26, 2001, the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus that has a fusing device that thermally fixes a developer image onto a recording medium.
2. Description of the Related Art
In the conventional art, an invention pertaining to control of the fusing parameters of the fusing device based on the thickness, size, conveyance orientation, conveyance interval, temperature, etc. of the paper, is disclosed in Japanese Laid-Open Patent Application H8-220929.
However, according to the fusing device disclosed in the above patent application, because changes in water content that occur due to changes in the environment or differences in the paper material are not taken into consideration, the problem exists that the toner image on the paper cannot be completely fused due to the fact that the thermal characteristics (such as the specific heat and heat capacity) of the paper change when the water content thereof changes because the material of the paper varies even if the thickness stays the same or when the moisture in the environment changes.
A main object of the present invention is to maintain good fusing performance of the fusing device in a stable fashion at all times regardless of the environment or the material comprising the recording medium.
In order to resolve the problem identified above, the image forming apparatus pertaining to the present invention includes a transfer member that transfers the developer image onto the recording medium, a fusing member that thermally fuses the developer image transferred by the transfer member onto the recording medium, a heating member that heats the recording medium, a detecting member that detects the temperature of the recording medium after it is heated by the heating member, and a controller that controls the output of the heating member based on the result of the detection by the detecting member.
The fusing member may have a first fusing unit and a second fusing unit that is located upstream from the first fusing unit in terms of the recording medium conveyance direction and that preheats the recording medium to a prescribed temperature before fusing is performed by the first fusing unit, and the controller may control the output of the second fusing unit.
The first fusing unit may comprise a flash fusing device.
The second fusing unit may also function as the heating member, and the detecting member may be located between the first fusing unit and the second fusing unit.
A paper conveyance controller may be included that moves the recording medium positioned at the second fusing unit forward and backward in the conveyance path when the temperature detected by the detecting member reaches or exceeds a prescribed temperature at the end of printing.
The heating member and detecting member may be located upstream from the transfer member in terms of the recording medium conveyance direction.
The detecting member may also detect the temperature of the recording medium before it is heated by the heating member, and the controller may control the output of the heating member based on the difference in the temperature detected by the detecting member of the recording medium before and after heating by the heating member.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description taken in conjunction with the accompanying drawings.